A small fishing town on an island would be ideal. Hard to keep secrets in, lots of superstitions, lots of boats and nets. And probably people would notice if a new girl showed up when Mara gets her legs.

The fishing net idea is good, and I like the isolation. She could have been freeing a dolphin or something and got tangled up instead. Perhaps there was a storm overnight which pulled the net free and washed it, and Mara, ashore?